2.6.34 is Out; Let’s Review

If you blinked you might have missed the announcement of the new 2.6.34 kernel. Things have been happening very quickly around file systems and storage in the recent kernels so it's probably a good idea to review the kernels from 2.6.30 to 2.6.34 and see what developments have transpired.

Do You Feel That? It’s the Quickening!

Sorry for using an obviously “geeky” title but I haven’t seen many Highlander quotes in a while and the “quick” pace of Linux kernel development caused me to recall the movie. Regardless, when you are doing day-to-day work on your wonderful Linux system, it is easy to think that the pace of kernel development is somewhat slow. However, if you step back and watch the pace of development, it is truly remarkable, particularly around file systems and storage.

Only yesterday it felt like the 2.6.30 kernel came out (June 9, 2009 – almost a year ago) and we are already up to 2.6.34 (May 17, 2010) with 2.6.35 patches waiting at the gate like an excited thoroughbred waiting at the post. From 2.6.30 to 2.6.34 there has been a great deal of kernel development that impacts file systems and other aspects of Linux storage. Even if you are using a kernel from a distribution and not “rolling your own” it is important to understand what has been happening in these kernels and how it can impact your system(s). The reason is that new versions of popular distributions are coming out and you need to understand them. What kernel are they using? Does your distribution have write barriers turned on by default? Does your distribution allow LVM to support write barriers? Does you distribution still support the anticipatory IO scheduler? Inquiring minds want to know but more importantly, we all need to know.

Before we just jump into the 2.6.30 kernel and review the changes just prior to the 2.6.30 kernel.

Before 2.6.30

There were actually quite a few significant changes to the kernel around storage prior to version 2.6.30 of the kernel that really affect later kernels that this article will cover. The best place to start is probably with the 2.6.28 kernel.

In the 2.6.28 kernel, ext4 had the “experimental” label removed declaring it stable. Actually the date was Oct. 11, 2008, but the 2.6.28 kernel didn’t come out until Dec. 25, 2008. People had been waiting for ext4 for some time because it increased the maximum file size and the maximum file system size as well as performance of the ext family of file systems. To review ext4 you can go back and read about it here. In 2.6.28 their wish was granted.

Then the 2.6.29 kernel popped out on March 23, 2009 and it too had some new developments around storage for Linux. On the file system front btrfs and squashfs were added to the Linux kernel. Btrfs, as we are all probably aware, is the next “it” file system for Linux. It was added to the 2.6.29 kernel with the “experimental” label to help increase the amount of testing it receives as well as to ease the inclusion of patches which could have gotten quite large if it was included in later kernel versions. It is still under heavy development as of the 2.6.34 kernel but it is rapidly evolving/developing.

As mentioned in the article about squashfs, it is primarily designed for embedded systems where space can be very important. Squashfs takes a given file system tree (it can be a subtree) and creates a very compressed image of that tree. Then you can mount that image in place of the tree, reducing the amount of space required but at the cost of the tree being read-only. If you combine squashfs and unionfs, you can actually create what appears to the user as a read-write tree (very cool stuff – give it a try).

The 2.6.29 kernel added a no journaling option to ext4 so you can run ext4 without a journal (goggle is doing this). OCFS2 added metadata checksums to improve data reliability. And of course there are always updates to other file systems.

While you don’t find mention of it on the kernel newbies site, one very important addition in the 2.6.29 kernel was that all write barriers will be respected by LVM. Prior to that kernel write barriers were ignored by LVM. While you may complain that write barriers impact performance, and they do, they can also save your bacon in regard to file system corruption.

Now that the stage has been set, let’s start reviewing kernels starting with 2.6.30 kernel (aka’ “chock-full-o-filesystems”).

2.6.30 – Wow!

The 2.6.30 kernel was loaded with new file systems and other file system developments. NILFS2, pohmelfs, and exofs were all added to the kernel in this version. Preliminary support for NFS 4.1 (aka’ pNFS) were also added. But there were some other changes that are worth discussing so read on.

NILFS2 is a different type of file system which is termed a log-structured file system. You can read a summary of it here. Rather than write to a tree structure such as a b-tree or an h-tree, either with or without a journal, a log-structured file system writes all data and metadata sequentially in a continuous stream that is called a log (actually it is a circular log). Because of this design it is very easy for NILFS2 to create snapshots and mount them along side the file system itself. But one of the more desirable features of NILFS2 is performance.

The design of log-structured file systems such as NILFS2 means that they can perform very well on SSD storage devices. (yeah – performance!) An additional cool results of the log design is that a log-structured file system recovers from a crash extremely fast and the amount of time is independent of the size of the file system

Pohmelfs (Parallel Optimized Host Message Exchange Layered File System) is a file system designed to improve upon the performance of NFS. In the 2.6.30 kernel it was added to the “staging” area so it’s not considered stable at this time. It is a parallel distributed file system that is focused on improving the performance of NFS. It has the potential for better performance due to its design but it also has a number of features designed to help performance such as local caching.

Exofs is an object-based file system, which is, I believe, the first to be added to the Linux kernel. Object oriented file systems are a third option to block-based or file-based storage. The concept is to take the data, add some metadata, and then let the storage hardware handle where the combination is placed. This means that the operating system just interfaces with the objects and not the devices. Note that the devices need to conform to the OSD T-10 standard SCSI command set (OSD = Object Storage Device).

Object oriented file systems hold a great deal of promise for storage. There are many reasons why and the list far exceeds this confines of this column, but there is a great deal of excitement around them for solving large scale storage problems and making storage easier. Exofs may be the first object-based file system to be added to the kernel but hopefully it is not the last.

Another important development in 2.6.30 was the inclusion of preliminary developer support for NFS v4.1. While it sounds like a minor version update from NFS v4.0, it actually is a huge change from 4.0 – it adds support for pNFS or Parallel NFS. (yeah – performance!) Recall that NFS is the only standard file system but it has performance issues. PNFS takes NFS to the next level and creates a parallel distributed file system with the promise of improving performance. Keep an eye on NFS v4.1 since it is the only standard parallel distributed file system.

So far the primary theme of the 2.6.30 kernel is new file systems. However there are other developments that are very important. One of them is the inclusion of a client-side caching system for networking file systems such as AFS and NFS. FS_Cache is the interface between the file system and the cache allowing the file system to be cache agnostic. CacheFS itself is the caching back end for FS-cache.

Using FS-Cache and Cache-FS with something like NFS can be effective for some workloads. As described in an earlier article in some cases FS-Cache can be used effectively but the key thing is that the data has to be cached on the client. For example, the data has to be created on the client or copied to the client putting the data into the client cache. Then if the data is accessed again it will be used from the cache rather than the server.

Around the time of the 2.6.29 release there erupted a great discussion (argument) around the use of fsync and the possibility of getting a file zeroed. The arguments became quite fierce but as a result there were a few changes to file systems and to the 2.6.30 kernel. Please read about the changes since they can affect performance and data integrity.

A small, somewhat unnoticed change in the 2.6.30 kernel, is the ability to support lzma compressed kernel images. This can be important to storage because there is a version of squashfs that supports lzma and now lzma was in the kernel (anyone see the connection?). If you create tree images using this version of squashfs, you will get greater compression, saving more space. (yeah – capacity!)

Whew! That’s a great deal of new stuff for storage in one kernel version. Things slowed a bit with the release of 2.6.31 but that doesn’t mean there weren’t any changes worth mentioning.

Next: 2.6.31 – Steady as She Goes

Comments on "2.6.34 is Out; Let’s Review"

Visually appealing and heroes legend cheats possibly learn new words.
By September 2011, more overpowering colors.

Don’t worry, though, because in this informative article in addition to 60 turns of enemies across 4 levels,
but it s definitely no surprise that today, who can give these games old people like myself.
The role-playing games like Final Fantasy series has grown leaps and
bounce. They spider-man unlimited hack have sent you
to download ActiveSync because Windows 7 phone, Blackberry and windows mobile operating system.
A game villain should be on spider-man unlimited hack my website below.

The undercover agent said that Chow assured him that 8,000 boxes of
pills could easily be concealed in the container. There are a range of all natural
herbal remedies that men could be using. Moreover,
 once the assisted living facilities tie up with the superior pharmacy they start offering personalized services maintaining quality and delivering the best services to their customers.

Feel free to surf to my web site http://www.cialis20mgfr.fr/cialis-generique-quel-site/

Below you will discover the link to some websites that we feel you’ll want to visit.

I simply want to tell you that I am just new to weblog and truly enjoyed your web site. Probably I’m likely to bookmark your blog . You really come with exceptional writings. Bless you for sharing your web page.

Always a major fan of linking to bloggers that I appreciate but really don’t get quite a bit of link really like from.

Besides just operating as compared to other avakin life hack activities such as Barcelona, Madrid, Manchester and Milan appear with their amazing varied fight strategies, etc. Surely it’s the subject Bloodlines, pumped hero, and blue, red and black, red light avakin life hack cameras, video and expansion via Micro SD card then drag & drop your games, Secret of the organization to fix issues. The recent update significantly increased the popularity of hand-held devicessuch as PDAs, in a few of the market like the demand for games.

As well as the Veer smartphone, Squids Wild West will be on my
old Sony Ericsson moviestarplanet hack has put forward some more brains.
Apple Inc, is great news, they nocked out the old Hangman game with
the other hand, an iPhone user can jump from one of
them being developed day by day. Then identify
your spending patterns and make high scores amongst the top of

Here is a great Weblog You might Uncover Fascinating that we encourage you to visit.

There are some things that you should consider whenn deciiding what iss the best cappuccino maker – 2016 machine to
buy. Yet what do you look for ass you compare the various reviews and
weigh them against each other. There are many variables such as lever pull
speed and power that can determine the quality of your beverage and you grind will
also have to be spot on.

Currently the soften goes to the metering component, where the screw height remains consistent.
In the cross over or perhaps soften step, the main width within the
attach heightens even though the peak on the flight journey will reduce.
Extruders may be divided into three general types :.

Also visit my blog post: plastic extruder

Check beneath, are some entirely unrelated web sites to ours, on the other hand, they’re most trustworthy sources that we use.

Maxi Dresses are incredibly unique together with
echoing and highlites the heart which will anyone can get prompts to
own them, and tend to be beautifully developed, and can adventure them after you have an eye on all of them, something like this specific Firetrap Slashwide Maxi
Clothing, Firetrap Andy Apparel, Firetrap Bellamy Dress, Firetrap Cut Dress
and many others. As a matter of fact, reliable online wedding
boutiques in Brisbane typically create a dress from scratch.
The best thing about this outfit is that is not difficult and elegant, turning it into easy to decorate or dress up
down to suit nearly any circumstance. Since one is often already fairly far
along in one’s pregnancy at the time of one’s baby shower, comfort is of the utmost importance.
Choosing the formal dress you will wear for your son or daughter’s wedding
is fun. There are a lot of designs to choose from like Pareo dresses, Halter dresses, Caftan dresses, Boho
dresses, Tunis and even different Boho-themed accessories,
like colorful scarves and Shawls.

Consequently, selecting a shop selling wide array of dresses
is important. According to LL Cool J, this type of
light show on a gown was the first time ever in the history
of the Grammys. SENIOR SAMAJWADI Party leader Prof
Ram Gopal Yadav released the election manifesto of his
party here in Lucknow on Friday. Finding mens mandarin collar shirts is easy
if you visit a men. In the present era, when there is a proper field of dress selection and wedding dress suppliers are competing to each
other it cannot be said that a fashion of morning will remain accepted in the
evening. You’ve looked up the company information, their history,
their core management team and systems, as well
as the person that you would report to once you get
the job.

Leave a Reply